The present invention generally relates to heat exchangers and, more particularly, to apparatus and methods of managing flow distribution into heat exchangers.
Heat exchanger life is driven by strain ranges and their location within the heat exchanger. These strain ranges are a function of the temperature gradients present, both spatial and temporal, as well as the heat exchanger design. The flow distribution into the heat exchanger is one factor driving the strain ranges and their location.
Current designs include a valve immediately upstream of the heat exchanger and which causes severe flow maldistribution. This, in turn, causes large spatial flow gradients, flow spikes locally that can exceed 10× uniform flow, and temporal flow gradients, as the valve opens and closes. The spatial gradients can also move to different locations on the heat exchanger entrance.
FIG. 1 is a plan view of a current design of a heat exchanger 10 and duct/manifold 11. A valve door 12 has a trailing edge 12a that, when nearly closed, allows a jetted flow 13 to enter the heat exchanger 10. This trailing edge design can cause large spatial flow gradients. It can also cause temporal gradients when the valve door moves 12 from one position to another. A large vortex 14 can also exist behind the valve door 12 and which can starve areas of the heat exchanger inlet 10a, such as in the area 15. FIG. 2 depicts, at the heat exchanger inlet, a flow distribution created by the design of FIG. 1.
As can be seen, there is a need for improved apparatus and methods to control flow maldistribution into a heat exchanger.